The present assignee has introduced heat exchangers that cool (and in some cases heat) saline that is sent in a closed loop through an indwelling heat exchange catheter for the purpose of maintaining patient temperature. The catheter can be used to prevent fever following ischemic insult or trauma or to induce therapeutic hypothermia for conditions such as stroke, heart attack (myocardial infarction), and cardiac arrest, as well as cooling for aneurysm surgery and warming after cardiac bypass operations, and other heating/cooling applications.
Of relevance to the present invention is the discovery that the medical outcome for a patient suffering from severe brain trauma or from ischemia caused by stroke, cardiac arrest, or heart attack is improved if the patient is cooled below normal body temperature (38° C.). As understood by the present invention, the medical outcome for many such patients might be significantly improved if the patients were to be moderately cooled to 32° C.-34° C. relatively quickly after an ischemic insult for a short period, e.g., 12-72 hours. It is believed that such cooling improves patient outcomes by improving the mortality rate, in that many organs can benefit from the cooling, and by improving the neurological outcome for those patients that survive.
As recognized in co-pending U.S. patent application Ser. No. 09/133,813, filed Aug. 13, 1998, owned by the present assignee and incorporated herein by reference, the above-mentioned advantages in treating ischemia by cooling can be realized by cooling the patient's entire body, i.e., by inducing systemic hypothermia. The advantage of systemic hypothermia is that, as recognized by the present assignee, to induce systemic hypothermia a cooling catheter or other cooling device need not be advanced into the blood supply of the brain, but rather can be easily and quickly placed into the relatively large vena cava of the central venous system. Moreover, since many patients already are intubated with central venous catheters for other clinically approved purposes anyway, providing a central venous catheter that can also cool the blood requires no additional surgical procedures for those patients. A cooling central venous catheter is disclosed in the present assignee's co-pending U.S. patent application Ser. Nos. 09/253,109, filed Feb. 19, 1999 and 09/305,613, filed May 5, 1999, both of which are incorporated herein by reference.
As mentioned above, it is believed that the sooner a patient is cooled after ischemic insult, the better the therapy. The present invention recognizes that many patients will have their first encounter with health care personnel in ambulances. Thus, it would be advantageous, as understood herein, to provide a means to cool these patients in the ambulance, with cooling continuing in the hospital. Heretofore, however, the heat exchangers that have been induced were not generally portable and in any case typically require AC power, both of which characteristics prevent their use in ambulances. With these recognitions in mind, the invention herein is provided.